This invention relates to rotary cutter assemblies of the type employed in earth boring applications and more particularly, this invention relates to rotary cutter assemblies employing rotary cone cutters for drilling wells, blastholes and the like.
Rotary cutter assemblies employing multiple rolling cutters which rotate relative to multiple axes of rotation in cooperating fashion to drill earth and hard rock formations are well known in the art. Many such prior art assemblies employ bit assemblies having legs or connector structures which carry the rolling cutters. Such cutter assemblies also provide means for conducting a flushing fluid from the drill string through the cutter assembly to the bottom of the drill hole. The heavy duty work environment for the rotary cutter assembly dictates that the assemblies be manufactured to incorporate a high degree of structural integrity. Conventionally, the connector structures and cutters are preassembled at a manufacturing location and permanently welded together to provide a rotary cutter assembly of an integral form which is then coupled to the drill string of the drill rig.
In the environment to which the rotary cutter assembly of the present invention is ordinarily subjected, adverse environmental conditions such as dirt, dust, shock, heat, and vibration frequently result in uneven wear or breakage of the multiple rolling cutters or the connector structures which constitute the drill bit assembly. It is not uncommon for one of the rolling cutters of the rotary cutter assembly to become non-functional, while the other rolling cutters of the assembly remain in functional condition. However, because the rotary multiple cutters operate in a cooperating fashion, an entire rotary cutter assembly may become non-functional due to either breakage or the wear of a single multiple cutter or portion thereof or of a single connector structure.
Recent attempts to ameliorate the harsh consequences of replacing an entire defective rotary cutter assembly have been directed to providing a rotary cutter having multiple components each of which can be readily replaced in the field. For example, in U.S. Pat. No. 4,335,794 issued to Robert D. Goodfellow, the inventor herein, and entitled "Rotary Cone Cutter", a multi-cone roller bit is disclosed wherein the rotary cone cutter is provided with individual releasable legs that permit replacement of a single defective rolling cutter unit without the requirement that the entire rotary cutter assembly be replaced. All of the releasable legs of U.S. Pat. No. 4,335,794 are clamped to a pot member by a single plug member so that all of the rolling cutter units are essentially clamped in place or released substantially simultaneously. The present invention is a new and improved rotary cutter assembly which provides improved means for efficiently replacing a rolling cutter unit of a cutter assembly on an individual basis, and also incorporates new and improved features relative to a fluid flushing system and desirable features of prior art rotary cutter assemblies.